Femtomolar limit of detection with a magnetoresistive biochip

Martins V.C., Cardoso F.A., Germano J., Cardoso S., Sousa L., Piedade M., Freitas P.P., Fonseca L.P.
INESC-MN Instituto de Engenharia de Sistemas e Computadores -Microsistemas e Nanotecnologias, IN-Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon, Portugal; IBB - Institute for Biotechnology and Bioengineering, Center for Biological and Chemical Engineering (CEBQ), Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal; Physics Department, Instituto Superior Tecnico, Av.Rovisco Pais, 1049-001 Lisbon, Portugal; INESC-ID Instituto de Engenharia de Sistemas e Computadores-Investigaçao e Desenvolvimento, Rua Alves Redol 9, 1000-029 Lisbon, Portugal; Electrical and Computer Engineering Department, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal

Abstract: In this paper the biological limit of detection of a spin-valve-based magnetoresistive biochip applied to the detection of 20mer ssDNA hybridization events is presented. Two reactional variables and their impact on the biomolecular recognition efficiency are discussed. Both the influence of a 250 nm diameter magnetic particle attached to the target molecule during the hybridization event and the effect of a magnetic focusing system in the hybridization of pre-labeled target DNA (assisted hybridization) are addressed. The particles carrying the target molecules are attracted to the probe active sensor sites by applying a 40 mA DC current on U-shaped aluminium current lines. Experiments comparing pre-hybridization versus post-hybridization magnetic labeling and passive versus magnetically assisted hybridization were conducted. The efficiency of a passive hybridization is reduced by about 50% when constrained to the operational conditions (sample volume, reaction time, temperature and magnetic label) of an on-chip real-time hybridization assay. This reduction has shown to be constant and independent from the initial target concentration. Conversely, the presence of the magnetic label improved the limit of detection when a magnetically assisted hybridization was performed. The use of a labeled target focusing system has permitted a gain of three orders of magnitude (from 1 pM down to 1 fM) in the sensitivity of the device, as compared with passive, diffusion-controlled hybridization. © 2009 Elsevier B.V. All rights reserved.
Author Keywords: DNA hybridization; Limit of detection; Magnetic focusing; Magnetic labels; Magnetoresistive biochip; Spin-valve

Year: 2009
Source title: Biosensors and Bioelectronics
Volume: 24
Issue: 8
Page : 2690-2695
Cited by: 10
Link: Scorpus Link
Document Type: Article
Source: Scopus
 Authors with affiliations:
  1. Martins, V.C., INESC-MN Instituto de Engenharia de Sistemas e Computadores -Microsistemas e Nanotecnologias, IN-Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon, Portugal, IBB - Institute for Biotechnology and Bioengineering, Center for Biological and Chemical Engineering (CEBQ), Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
  2. Cardoso, F.A., INESC-MN Instituto de Engenharia de Sistemas e Computadores -Microsistemas e Nanotecnologias, IN-Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon, Portugal, Physics Department, Instituto Superior Tecnico, Av.Rovisco Pais, 1049-001 Lisbon, Portugal
  3. Germano, J., INESC-ID Instituto de Engenharia de Sistemas e Computadores-Investigaçao e Desenvolvimento, Rua Alves Redol 9, 1000-029 Lisbon, Portugal
  4. Cardoso, S., INESC-MN Instituto de Engenharia de Sistemas e Computadores -Microsistemas e Nanotecnologias, IN-Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon, Portugal, Physics Department, Instituto Superior Tecnico, Av.Rovisco Pais, 1049-001 Lisbon, Portugal
  5. Sousa, L., INESC-ID Instituto de Engenharia de Sistemas e Computadores-Investigaçao e Desenvolvimento, Rua Alves Redol 9, 1000-029 Lisbon, Portugal, Electrical and Computer Engineering Department, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
  6. Piedade, M., INESC-ID Instituto de Engenharia de Sistemas e Computadores-Investigaçao e Desenvolvimento, Rua Alves Redol 9, 1000-029 Lisbon, Portugal, Electrical and Computer Engineering Department, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
  7. Freitas, P.P., INESC-MN Instituto de Engenharia de Sistemas e Computadores -Microsistemas e Nanotecnologias, IN-Institute of Nanoscience and Nanotechnology, Rua Alves Redol 9, 1000-029 Lisbon, Portugal, Physics Department, Instituto Superior Tecnico, Av.Rovisco Pais, 1049-001 Lisbon, Portugal
  8. Fonseca, L.P., IBB - Institute for Biotechnology and Bioengineering, Center for Biological and Chemical Engineering (CEBQ), Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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